Cloud

Introduction

Since the emphasis on the cloud technologies have risen over the recent times, a wide variety of tools, technologies, languages have entered in the cloud space. One of the is Terraform. Terraform has become one of the top choices for dev ops engineers as far as infrastructure level code is concerned. In this post you will come across all types of important interview questions being asked when you are interviewed on Terraform. Lets get started.

What is Infrastructure as Code or IAC

As the name says, Infrastructure as code, it means creating your infrastructure with the help of code. Instead of creating the infra by web UI, people have started creating the infrastructure via code. Searching through so many options and creating an S3 bucket or an EC2 instance through UI is more complex than writing code which is even simpler. I have written an elaborate blogpost on Infrastructure as code.

What is your understanding on Terraform

Terraform is used to automate and manage your infrastructure, your platform, and services that run on the platform. Terraform is Infrastructure as a code tool that you can use to work with any of the the current available cloud providers platforms. Terraform is open source and uses Hashicorp configuration language (HCL) to define resources. Terraform makes sure that whatever code you write it will make sure that it will call the corresponding cloud provider API’s and provision those resources. Sometimes the properties can be different because each cloud provider probably expects is own unique set of values to provision a source. We write code for multiple cloud providers in the same file and Terraform is responsible to create the resources with the right cloud providers.

What are the features of Terraform

Terraform is open source.
Terraform is used to describe your infrastructure in declarative configuration files that are human-readable.
Implementing multi-cloud deployment environment is possible with less efforts.
We can automate the infrastructure management using Terraform.
Terraform’s execution plan will ask for the final user consent before making any change to the infrastructure. This enables the user to evaluate the change one last time.
Terraform has the ability to translate the Hashicorp configuration language (HCL) into Json.

Explain the workflow of the core terraform

Write – Create infrastructure in the form of code.
Plan – This step will plan ahead of time to see how the changes look before they are implemented.
Apply – Create a repeatable infrastructure.

What are the components present in Terraform architecture

Following are the components present in Terraform architecture.

CLI (Command Line interface)
Graph Walk
Graph Builder
State Manager
Sub-graphs
Expression Evaluation
Vertex Evaluation
Configuration Loader
Backend

What are the most frequently used Terraform commands

Below are some of the most frequently used Terraform commands

version
show
fmt
init
validate
plan
apply
destroy
output
state

What is the purpose of Terraform in Devops

Terraform helps DevOps teams to define and enforce infrastructure configurations across multiple clouds and on-premises data centers.

What is Terraform init

Terraform init is used to initialize the current directory as a working directory where all the Terraform configurations files are present.

Syntax :

terraform init [options]

How to define a null resource in Terraform

Sometimes it’s useful to have a resource that effectively creates nothing. Terraform provides such a resource called a null resource. A null resource is particularly useful for debugging modules. By adding a null resource, we can quickly echo out variables or runs.

The null_resource resource implements the standard resource lifecycle but takes no further action. The triggers argument allows specifying an arbitrary set of values that, when changed, will cause the resource to be replaced. A null resource behaves like any other resource, you can configure provisioners, connection details, and other meta-parameters just like any other resource. This gives you more precise control over when provisioners execute in the dependency graph.

What is Terraform cloud

Terraform Cloud is software that enables teams to work together on Terraform. It provides features such as easy access to shared state and secret data, access controls for approving infrastructure changes, a private registry for sharing Terraform modules, detailed policy controls for governing the contents of Terraform configurations, and more to ensure that Terraform runs in a consistent and reliable environment.

Terraform Cloud is a hosted service that can be found at https://app.terraform.io. Terraform allows small teams to connect to version control, share variables, run Terraform in a reliable remote environment, and securely save remote state for free. Paid tiers provide you with the ability to add more than five people, establish teams with varying levels of access, enforce policies before building infrastructure, and work more efficiently.

What is Terraform backend

A backend defines where Terraform stores its state data files. By default, Terraform uses a backend called local which stores state as a local file on disk. Terraform keeps track of all the resources created in a state file

What are the alternatives of Terraform available in the market

Ansible
Kubernetes
Azure Management Tools.
Morpheus.
CloudHealth.
Turbonomic.
CloudBolt.
Apptio Cloudability
Platform9 Managed Kubernetes.

What do you mean by Terraform CLI and some of the basic Terraform commands

The Terraform Command-Line Interface (CLI) is used to manage infrastructure and interact with Terraform state, configuration files, providers, etc.

What are Terraform modules

Modules can be thought of as a container consisting of various resources that work in collaboration. The root module includes resources mentioned in the .tf files and is required for every Terraform.

What is private module registry in Terraform

Private module registry in Terraform helps you to share Terraform providers and Terraform modules across the organization. It supports versioning and supportable list of available providers and modules. We can also apply rules on the registry which specifies how many members in the organization can use the modules.

Can we use Terraform for on premise infrastructure

Yes. we can use Terraform for on premise infrastructure

Name some of the built-in provisioners available in Terraform

Below are some of the built-in provisioners available in Terraform

Salt-masterless Provisioner
Puppet Provisioner
File Provisioner
Chef Provisioner
Remote-exec Provisioner
Local-exec Provisioner
Habitat Provisioner

What is destroy command in the context of Terraform.

Terraform destroy command destroys the previously-created infrastructure or this command is used to quickly clean up all of those temporary objects.

terraform destroy [options]

Explain the usage of terraform validate command in the context of Terraform.

Terraform validate command is used to verify whether the configuration is valid or not. Validate checks if a configuration is correct syntactically. It is used for general verification of reusable modules, such as ensuring that attribute names and value types are correct. This command can be executed automatically, for example as a post-save check in a text editor or as a test step for a reusable module in a continuous integration system.

Syntax:

terraform validate [options]

Explain the command terraform apply in the context of Terraform.

Terraform apply is used to create or update the infrastructure. This command is used in conjunction with the plan file.

Syntax:

terraform apply [options] [plan file]

Explain the command terraform version in the context of Terraform.

Terraform version command is used to see the current Terraform version as well as any installed plugins.

Syntax:

terraform version [options]

Explain the command terraform taint in the context of Terraform.

The terraform taint command informs Terraform that a particular object has become degraded or damaged. Terraform represents this by marking the object as “tainted” in the Terraform state, and Terraform will propose to replace it in the next plan you create.

Since this command is deprecated, it is recommended to use -replace option with terraform apply.

Syntax:

terraform taint [options] address

Explain the command terraform fmt in the context of Terraform.

The terraform fmt is used to rewrite Terraform configuration files to a canonical format and style. Other Terraform commands that generate Terraform configuration will produce configuration files that conform to the style imposed by terraform fmt, so using this style in your own files will ensure consistency.

Syntax:

terraform fmt [options] DIR

What is the command to destroys Terraform managed infrastructure

Below command is used to destroys Terraform managed infrastructure.

Syntax:

terraform destroy [options]

What is resource graph in Terraform

Resource graph in Terraform is used to provide visual representation of the resources. It helps in creating or modifying independent resources. Terraform generates plans and refreshes the state by creating a plan for the graph’s configuration. It promptly and successfully builds structure to assist us in understanding the drawbacks.

What do you mean by Sentinel in Terraform

Sentinels are a powerful way to implement a variety of policies in Terraform. Some of the examples are as below.

Restrict roles the cloud provider can assume
Forbid only certain resources, providers, or data sources
Enforce explicit ownership in resources
Review an audit trail for Terraform Cloud operations
Enforce mandatory tagging on resources
Restrict how modules are used in the Private Module Registry

What is the way to store sensitive data in Terraform

Saving sensitive information like credentials in plain text on local drive or in the code repo can be very risky. We should use encrypted storage in order to store all your passwords, TLS certificates, SSH keys, etc.

What is State File Locking

State File Locking is used in order to prevent state file corruption. State file corruption happens when multiple users are doing the same task by blocking activities on a given state file. When a particular user releases the lock, only then the other one can operate on that state.

Explain Terragrunt and its uses

Terragrunt is a lightweight wrapper that adds extra features for maintaining DRY (Don’t Repeat Yourself) configurations, dealing with many Terraform modules, and managing remote state.

Terragrunt is used for

Keeping the Terraform code DRY
Keeping our CLI flags DRY
Working with multiple AWS accounts
Executing Terraform commands on multiple modules
Keeping the remote state configuration DRY

What is Tainted Resource in Terraform

When an object is degraded or damaged and when you want to notify Terraform about it, then we run below command.

terraform taint [options] address

Terraform represents it by marking the object as tainted in the Terraform state, and Terraform will replace it in the next plan whenever it is created. Complete and latest information about this command can be found in this link

Explain what is Terraform Core

Terraform Core is a statically compiled binary written in Go programming language. The compiled binary is the command line tool (CLI), the entrypoint for anyone using Terraform. The code is open source and hosted at github.com/hashicorp/terraform.

The primary responsibilities of Terraform Core are:

Infrastructure as code: reading and interpolating configuration files and modules
Resource state management.
Construction of the Resource graph.
Plan execution.
Communication with plugins over RPC.

How to upgrade plugins in Terraform

terraform init -upgrade

-upgrade option is used to upgrade modules and plugins throughout the installation process. This command rechecks the releases.hashicorp.com to find new acceptable provider versions. It also downloads available provider versions.

Differentiate between Terraform and Cloudformation.

	Terraform	Cloudformation
Platform Support	Terraform supports various cloud providers such as AWS, GCP, Azure etc	CloudFormation is limited to AWS services
Language support	Terraform makes use of HCL language (Hashicorp Configuration Language). This language is also JSON compatible.	CloudFormation uses either JSON or YAML as a language.
Cost	Open source and completely free. Also has premium enterprise version.	Completely free. The only expense that consumers pay is for the AWS service that CloudFormation provides.

Differentiate between Terraform and Ansible.

Terraform	Ansible
Terraform is a tool that is designed to help with the provisioning and deprovisioning of cloud infrastructure using an infrastructure as code method.	Ansible is a more general configuration tool.
Terraform is a tool used for creating and managing IT infrastructure.	Ansible automates provisioning, deployment, and other IT processes.
It uses the declarative approach.	Ansible automates provisioning, deployment, and other IT processes. It uses the procedural approach.
It’s ideal for orchestrating cloud services and building cloud infrastructure from the ground up.	It is mostly used to configure servers with the appropriate software and to update resources that have previously been configured.

What is Blue Green deployment

September 1, 2022 by Ravikiran Kada Leave a Comment

Introduction

One of the activity that every developer wishes, is hassle free application deployment so that they don’t have sleepless nights due to deployment failure 😋😂. Specially in the large teams and business units, when there are hundreds of microservices, the deployment task has to be carried out very cautiously. If the deployment fails due to any reason, be it wrong application configuration or any other issue, we should have rollback strategy in place, so that application can be brought back stable state.

Traditional application Deployment

In the traditional deployment, if there was any deployment failure, the previous stable version of the application was being deployed. Sometimes rollback is not easy because we need to perform all the activities from scratch. In the worst case the application is unavailable for long periods of time.

In order to avoid all the havoc, we need to have proper deployment strategy in place. In this post we will discuss one of the many deployment strategies i.e. Blue Green Deployment.

Blue Green Deployment

A Blue Green deployment is a deployment strategy which consists of two live production environments at the same time that are identical to each other. In this deployment strategy, the role of live production can either be Blue or Green. Lets consider Blue as the current production application present in production, and green as the new version that is to be deployed. The main goal of this strategy is to reduce the downtime of the application so that no business user is impacted.

Blue environment consists of the live production application. After adding a additional features to your application you deploy it to the Green Environment. In order to test if existing features as well as the new features are working fine, you allow some part of the applications traffic (1% or any criteria of your business domain say user Id) to the green environment. After successful testing either gradually increase the traffic or switch over the Green environment as the live production environment. In case of any failures you can rollback to the previous stable version i.e. Blue.

When you have new set of features ready for your next release, you switch from green to blue like you did from blue to green earlier. That way both green and blue environments are playing the roles of live and rollback versions.

From the database standpoint, the deployment strategy can be tricky. The priority should be given to database schema changes (if any) first which supports the Blue as well as Green version. The rollback version should be tested first, if everything is fine then deploy the new version of application. If testing was successful with the new production version, then the next task would be to remove the database support for the old version of the application.

Blue Green deployment on Pivotal Cloud Foundry(PCF)

Lets talk about blue green deployment in Pivotal Cloud Foundry. CF Router plays a major role of switching the traffic between Blue and Green versions of the application. All we have to do is Map or Unmap the route (URL) to Green or Blue based on the verification done for your application flows.

For more detailed information, you can go over the official documentation by Pivotal.

Blue Green deployment on Amazon Web Services (AWS)

In AWS, there are are components which contribute or work together to achieve Blue Green deployment strategy. For detailed and well explained documentation, you can go over the official AWS blue green deployment guide.

I hope you liked this post. Please do share across the community so that everyone will have a good time learning. Please feel free to comment if you find anything to be corrected in the post.

What Are Kubernetes Persistent Volumes

February 14, 2022 by Ravikiran Kada Leave a Comment

In the early days of computers, people used the term “volume” a lot. This was the term referred to the computer hard drive. It is where all your data is stored. Let me set the context by explaining a simple example. While working on Spring boot with H2 database (in-memory database) at your local IDE level, whenever we perform CRUD operations against the database, the data will be wiped out when you restart your spring boot application. Obviously in production environment/scenario we will use others databases like Oracle/Mysql/Postgresql and we will ensure that the system is a highly available.

In Kubernetes terms, lets say you have a MySQL pod where the data is stored, the data will be wiped out when you restart the pod. In the kubernetes architecture, you have to take care of your applications data store requirements. In short, the data storage should not be dependent on the POD lifecycle nor the cluster state in the event of crash.

Data storage requirements can be anything from database to storing files in a directory.

To sum up in a single line, Kubernetes Persistent Volume is a component in Kubernetes architecture, which is just like a cluster resource which helps with the storage requirements of the containers in the pod. Just imagine if Volumes wouldn’t exist, the data which containers created would be lost if the containers died 😶 This is the reason why there was a need for a separate component in the kubernetes cluster i.e. Persistent Volumes. Now that you have some idea about Persistent volumes, lets explore each aspect.

Characteristics of Volumes

Since the data is an essential component that your applications relies on, volumes should be highly available in nature.
Even if the cluster dies or crashes completely the Persistent Volumes needs to stay intact.
Volumes should be available to all the nodes.

Persistent Volumes (PV)

Persistent volumes are just an abstract component or an interface, the actual storage will be taken care by various cloud providers such as AWS, Azure etc. Actual storage can be actual physical storage from local Hard disk drive of the cluster node or NFS servers outside the cluster. Persistent volumes gets created by using kubernetes yml file. In this file we can specify various properties like the storage provider, storage volume etc

You can take a look at the list of Persistent Volumes that kubernetes supports. Lets look at one example of Persistent volume yaml file configuration.

I hope you liked the post. Happy Learning 😊

What is Infrastructure as Code (IaC)

February 9, 2022 by Ravikiran Kada 1 Comment

Introduction

As the name says, Infrastructure as code, it means creating your infrastructure with the help of code. Now you might think if I can create the resources and design my infrastructure by signing into my cloud providers account such as AWS, Google etc which is super easy and interactive, then why do I have to write code for this as well? As we go along the post we would be uncovering the real benefits of creating you infra via code vs the web UI 😊

Lets take an example of AWS in this post. There was a reason behind Amazon creating AWS to support their growing business in various horizons and as days went by, AWS became one of the go to place for many major organisation for cloud solutions. At the time of writing this post, AWS stands as the most profitable business for the Amazon. But here come a twist, at least what I feel after logging into my AWS account, I kind of go lost as to where to start from. So many options and wide variety of services that AWS provides that you tend to keep searching for things. After so much struggle lets say you manage to setup your development environment by spinning up a bunch of EC2 instances, setting up queues, database, S3 buckets etc etc, As days pass by, now you have to setup you new UAT environment 🥺 . As of writing this post, I have noticed that AWS sometimes change their UI as well as change some options here and there.

Nowadays instead of creating the infra by web UI, people have started creating the infrastructure via code. Instead of searching through so many options and creating an S3 bucket or an EC2 instance through UI , writing code is much more simpler

Benefits of Infrastructure as code (IaC)

Configuration Consistency and Resuse

We can create an environment using the same set of configuration used for initial environment setup. Chances of human error for environment setup would be less as compared to creating via the web UI. If you have done this using UI, you would tend to forget some setup steps. Imagine if there was no code, the engineer sets up the complex environment and left the organization some day. Imagine how difficult it would be for the new engineer to figure out how it was setup.

Infrastructure Automation

We are automating the whole process of infrastructure rather than using the manual steps to configure via the Web UI. This reduces the risk on human error.

GitOps

Not only are we creating infra via code, but this code is being maintained in version control system. It will be leveraged or improved by multiple people. Once we push the new changes, build pipeline is run which provisions the infra for you, hence this becomes he part of the build process. Same process of code reviews and pull requests can be followed here as well like we do for our application code base. We can change back and forth with the versions maintained if there are any issues with the infra.

Terraform

Terraform is Infrastructure as a code tool that you can use to work with any of the the current available cloud providers platforms. Terraform is open source and uses Hashicorp configuration language (HCL) to define resources. Terraform makes sure that whatever code you write it will make sure that it will call the corresponding cloud provider API’s and provision those resources. Sometimes the properties can be different because each cloud provider probably expects is own unique set of values to provision a source. We write code for multiple cloud providers in the same file and Terraform is responsible to create the resources with the right cloud providers.

I hope you liked this post. Happy Learning 😊

What are Pods in Kubernetes

January 4, 2022 by Ravikiran Kada Leave a Comment

Introduction

Pod is one of the most important object in Kubernetes and it consists of containers. Pod can contain one or more containers in it. Related containers are grouped into a single Pod. In the image below there are 2 pods. In the first pod we have mongodb, bank account opening application and bank money transfer application. In the second pod we have postgresql, credit card processing application and home loan application. The job of a Pod is to provide all the resources that are necessary for these containers to work. Resources can be Security management, Configuration management, Volumes to store data etc.

In the similar way we can have multiple pods according to the use case.

A good practice is to have a single container in a pod. There are multiple ways to create a pod, and we can replicate a single pod.

Pod Lifecycle

Pending – This is the first phase of a POD, as soon as you create the pod the status assigned is Pending. API Server present in the master node will look at the pod configuration and check if everything is correct, then it will create an entry in the etcd. After this it will ask the worker node to create a pod as requested. But, one or more container’s setup is still is process and is in the process of being ready.

Running – The Pods that we have created will be scheduled in one of the worker node in the cluster. When at least one container within the pod is running.

Succeeded – The pod has performed the task, all the containers within it have terminated successfully and they wont restart.

Failed – When every container within the pod has terminated, but one or more containers have exited with some failure code , in that case the pod will be in a failed state.

Unknown – If for some reason the pod status could not be fetched by the master node then the status is set as Unknown.